PET container for foods and drinks containing recycled resin and having DLC coating film formed on surface thereof

ABSTRACT

A PET container for foods and drinks having a DLC coating film formed on the inner surface thereof, characterized in that the PET container for foods and drinks is produced by the use of a molding material comprising a mixture of a recycled resin which is originated from a used PET container for foods and drinks and has not subjected to a treatment for adjusting its intrinsic viscosity with a fresh PET resin. The above PET container for foods and drinks can provide satisfactory barrier properties against a pollutant substance being present in a resin.

This application is a divisional application of Ser. No. 10/149,336,filed Jun. 6, 2002.

TECHNICAL FIELD

The present invention is related to a plastic container adapted for useas a food container or the like, and in particular to a plasticcontainer containing recycled PET resin which makes it possible for theresin of a used PET (polyethylene terephthalate) container for foods andbeverages to be recycled and used again as a plastic container for foodsand beverages, and a manufacturing method thereof

PRIOR ART TECHNOLOGY

Japanese Laid-Open Patent Publication No. HEI 8-53117 discloses a vapordeposition apparatus which uses CVD (Chemical Vapor Deposition, chemicalvapor growing method), in particular, a plasma CVD method to vapordeposit a DLC (Diamond Like Carbon) film on the inner surface of aplastic container in order to improve the gas barrier properties and thelike of containers such as containers for carbonated beverages and highfruit juice beverages and the like. Further, Japanese Laid-Open PatentPublication No. HEI 10-258825 discloses a manufacturing apparatus formass producing a DLC film coated plastic container, and a manufacturingmethod thereof. Furthermore, Japanese Laid-Open Patent Publication No.HEI 10-226884 discloses a manufacturing apparatus which makes itpossible to apply a coating of DLC film without mottling to a containerhaving protrusions which protrude from the outer surface to the outside,and a manufacturing method thereof.

A DLC film is a film called an i-carbon film or an amorphous carbonhydride film (a-C:H), and also includes a hard carbon film. Further, aDLC film is an amorphous-state carbon film, and includes SP³ bonding andSP² bonding.

Incidentally, the estimated resource recycling rate of PET containers inJapan for 1999 was 18%, and the use thereof was 70% for fiber products,and 20% for sheet related products used for trays and egg packs and thelike for packaging apples and pears and the like. These fiber productsand sheet related products have a low added value, and the resourcerecycling rate is influenced by the market conditions and the like ofthe fiber industry. Hereafter, the PET container recycling rate isexpected to improve in view of the building of a recycling society, andthere is a demand for fundamental users of PET container recycledproducts. For this reason, there is a desire to use PET containers inrelated industries, namely, to build a bottle-to-bottle self-completetype recycling system to carry out recycling of containers.

SUMMARY OF THE INVENTION

However, in the case where a used PET container is recycled and usedagain as a food container, the recycled product is required to have noproblem in point of the sanitary safety of food, and even when it isassumed that the sanitary safety of a recycled product is the same asthat of a new product, the consumer or user of the recycled productneeds to be convinced. Further, with regard to the recycled producthaving no problem in point of sanitary safety of food, the approval andthe like of a related government agency including an evaluation methodthereof are required. Accordingly, at the present time, the use ofrecycled products for food containers is in a uneasy state.

A more detailed examination of the thought process of sanitary safetywhen recycled PET containers are used for food container packages isdescribed below. Namely, in general after a food container package isconsumed/used for the original purpose, due to contact with a foreignsubstance and foreign substance mixing and the like in the use foranother purpose, unexpected misuse, or discarding/recycling process, arisk of contamination is expected due to the unknown substance.Accordingly, in order for it to be possible for a container to berecycled and used again as a food container package, such unknowncontaminants inside the recycled product must be reduced by therecycling process to a level that makes it possible to ensure sanitarysafety, namely, below the allowable reference value of contamination. Inorder to make it easy for the unknown contaminants to be reduced belowthe allowable reference value, {circle over (1)} the discarding sourceof the reclaimed/recycled waste plastic needs to be restricted as muchas possible, and the origin thereof needs to be made clear (sourcerestricting) in order to prevent as much as possible the waste plasticthat forms the source material from being contaminated by unknownsubstances; {circle over (2)} a method of use needs to be devised tomake it possible to ensure a safe level at the time of use even when,for example, some contaminants remain after recycling; {circle over (3)}a recycling performance needs to be provided to make it possible towash/reduce contaminants to a safe level even when contamination occursdue to some kind of unknown contaminants (ensuring recyclingperformance); {circle over (4)} a means needs to be conceived to preventcontaminants from eluting into the contents even when a small amount ofunknown contaminants remain; and the like need to be carried out.

With regard to {circle over (1)} described above, this is a problemsolved by the building of a societal recycling system, and with regardto {circle over (2)}, a solution is carried out by restricting themethod of use from the viewpoint of the type of foods, the usetemperature, the use time, the contact surface area, the use and thelike. With regard to {circle over (3)}, a method has been proposed inwhich used resin is first decomposed to a low molecular level, and thenpolymerization is carried out again to form a resin.

However, with regard to the system of {circle over (1)}, it is built atthe same time recycled products flow to market, and with regard to{circle over (2)}, it is difficult to find fundamental users of recycledproducts as restrictions are made to use. With regard to {circle over(3)}, the required cost for the process of low molecular conversion ofresin is high, and becomes disadvantageous by a cost comparison with newresin. Accordingly, the {circle over (4)} conception of a means toprevent contaminants from eluting into the contents even when a smallamount of unknown contaminants remain is thought to be realistic.

The means for preventing contaminants from eluting into the contents islargely separated into two kinds. As for one of these, for example, bysandwiching both surfaces of a recycled PET resin layer between new PETresin layers to create a laminated structure, the contents are preventedfrom making direct contact with the recycled PET resin layer, and thisforms a method for preventing the movement of contaminants. The othermeans is a method in which, after a container is molded from only a basesubstance which contains recycled PET resin, the inner wall surface ofthe container which makes contact with the contents is coated or thelike with a barrier layer that prevents the permeation of contaminants.The former means is disadvantageous because a high cost is required formolding.

The present invention is related to technology for forming the latterbarrier layer which does not have a high cost, and because contaminantswill elute into the container contents in a container that is obtainedby simply molding resin containing recycled PET resin, it is an objectthereof to make it possible to reuse used PET containers for foods andbeverages by coating the inner surface of the containers with a DLC filmto provide the containers with contaminant elution barrier properties,and by making it possible to reuse PET containers, placing the resin ofused PET containers for foods and beverages in a recycling route.Additionally, it is an object of the present invention to reuse theresin of used PET containers for foods and beverages without requiringexcessive cost, namely, without carrying out a solid phasepolymerization process on the resin of used PET containers.

It is a second object of the present invention to provide a DLC filmcoated PET container for foods and beverages containing recycled resinhaving an optimal compounding ratio, with consideration given to thebalance between the utilization factor of used PET containers for foodsand beverages and the performance of PET containers for foods andbeverages containing recycled resin. The background for consideringbalance comes from the following facts: {circle over (1)} if the resinof a used PET container for foods and beverages which does not undergo asolid phase polymerization process has an excessive compounding ratio,it will be difficult to maintain the container strength and ensuremoldability; and {circle over (2)} there is a demand to minimize theeffects of colored impurities contained in the resin of used PETcontainers for foods and beverages.

It is a third object of the present invention to provide a PET containerfor foods and beverages containing recycled resin coated with a DLC filmhaving sufficient contaminant elution barrier properties andsatisfactory fundamental container properties such as gas barrierproperties and the like.

It is a fourth object of the present invention to provide a method ofmanufacturing DLC film coated PET containers for foods and beveragescontaining recycled resin having sufficient container strength andsufficient contaminant elution barrier properties, in which inexpensivepelletized material is used without carrying out a solid phasepolymerization process on the resin of used PET containers for foods andbeverages, and sufficient mixing with unused PET resin pellets iscarried out to make it possible to mold containers.

Further, the container according to the present invention includescontainers used with a cover or plug or seal, and also containers usedin an open state without the use of such sealing members. The size ofthe opening is determined in accordance with the contents. Plasticcontainers include plastic containers having a prescribed thickness andmoderate stiffness, and plastic containers formed from sheet materialwhich is not stiff. Further, this includes the cover of the container.The contents of the plastic container according to the present inventionparticularly concern beverages such as carbonated beverages or fruitjuice beverages or soft drinks or the like.

In order to achieve the objects described above, the present inventordiscovered the following inventions. Namely, in the DLC film coated PETcontainer for foods and beverages containing recycled resin of thepresent invention, a DLC film is formed on the inner surface of the PETcontainer for foods and beverages, wherein the PET container for foodsand beverages is a container molded from a molding material comprising amixture of recycled resin of used PET containers for foods and beverageswhich has not undergone intrinsic viscosity adjustment, and unused PETresin.

Further, in the DLC film coated PET container for foods and beveragescontaining recycled resin of the present invention, the compoundingratio (weight of recycled resin of used PET containers for foods andbeverages which has not undergone intrinsic viscosity adjustment/(weightof recycled resin of used PET containers for foods and beverages whichhas not undergone intrinsic viscosity adjustment+weight of unused PETresin)) of said mixture is preferably greater than 0 but less than 0.40.

Furthermore, in the DLC film coated PET container for foods andbeverages containing recycled resin of the present invention, the oxygenpermeability is preferably less than or equal to 0.010 ml/day/containerwhen converted to a 500 ml volume.

The method of manufacturing a DLC film coated PET container for foodsand beverages containing recycled resin according to the presentinvention comprises the steps of shredding used PET containers for foodsand beverages to form flakes, and after removing foreign material fromsaid flakes, washing said flakes using an alkaline washing agent andwater, and drying said flakes to obtain washed flakes; obtainingrecycled resin pellets which have not undergone intrinsic viscosityadjustment from said washed flakes; molding a container containingrecycled resin using said recycled resin pellets and unused PET resinpellets adjusted so that the compounding ratio (weight of recycled resinpellets/(weight of recycled resin pellets+weight of unused PET resinpellets)) is greater than 0 but less than 0.40; and coating the innersurface of said container with a DLC film so that the oxygenpermeability of said container is less than or equal to 0.010ml/day/container when converted to a 500 ml volume.

The plastic container according to the present invention means a PETcontainer for foods and beverages, and in particular a PET container forfoods and beverages containing recycled resin. The method ofmanufacturing this PET container for foods and beverages containingrecycled resin is as follows. Used PET containers for foods andbeverages are shredded to form fine flakes, foreign material is removed,and then the flakes are washed until clean using an alkaline washingagent and water. These washed and dried flakes are pelletized by apelletizer. These pellets of the used PET resin for foods and drinkspelletized in this way are mixed with unused PET resin, and a containeris manufactured using a molder. At the container molding time, thecompounding ratio (weight of recycled resin of used PET containers forfoods and beverages which has not undergone intrinsic viscosityadjustment/(weight of recycled resin of used PET containers for foodsand beverages which has not undergone intrinsic viscosityadjustment+weight of unused PET resin)) of these pellets should begreater than 0 but less than 0.40, and preferably greater than 0 butless than or equal to 0.30. The utilization factor of used PET for foodsand beverages is preferably high, and the performance of the PETcontainer for foods and drinks containing recycled resin is alsopreferably high, but when considering a balance of both of these, themost preferred compounding ratio is greater than or equal to 0.10 butless than or equal to 0.20. When the compounding ratio is 0, it is notpossible to recycle used PET container resin. On the other hand, becausethe intrinsic viscosity (IV) of the pellets of the used PET resin forfoods and beverages is low in comparison with the intrinsic viscosity ofunused PET pellets, when the compounding ratio is greater than or equalto 0.40, the container strength goes down, and when an excessive amountof low intrinsic viscosity PET pellets are mixed in, it is difficult tomold PET containers. In such case, by carrying out solid phasepolymerization to raise the polymerization degree of the pellets of theused PET resin for foods and beverages, and by adjusting the molecularweight of the used PET resin for foods and beverages, it is possible fora container to use 100% used PET resin for foods and beverages. However,because a rise in manufacturing costs accompanies the carrying out ofsolid phase polymerization, container molding is preferably carried outby mixing used PET resin which has not undergone intrinsic viscosityadjustment and unused PET resin.

Further, the transparency/clearness of the PET container for foods andbeverages containing recycled resin is lowered by colored impuritiescontained in the pellets of the used PET resin for foods and beverages.When an overall judgment of the above facts is made, the maximumcompounding ratio should preferably not exceed 0.40.

As is understood by referring to the embodiments described below, in thePET container for foods and beverages containing recycled resin obtainedin this way, one portion of contaminants contained in the pellets of theused PET resin for foods and beverages will elute into the containercontents. Accordingly, PET containers for foods and beverages containingrecycled resin can not be reused for foods and beverages in a statewhere only molding is carried out.

In this regard, in the present invention, the inner surface of thecontainer is coated with a DLC film to prevent elution of contaminants.The reason for choosing a DLC film is that a DLC film has superiorperformance in following the expansion and contraction of the containerwhen compared with a SiO_(x) film or the like, and in particular thischoice is due to the consideration given to the case where the containeris filled with beer, carbonated beverages, fruit juices or the likewhich cause large expansion and contraction of the container. Further,properties such as gas barrier properties and the like are changed bythe composition and film thickness and the like of the DLC film.Accordingly, in the present invention, the judgment of whether or notthe DLC film has sufficient contaminant elution barrier properties isdetermined by indicating the oxygen gas barrier properties of the entirecontainer, and the oxygen permeability of the DLC film coated PETcontainer for foods and beverages containing recycled resin is indicatedas being less than or equal to 0.010 ml/day/container when converted toa 500 ml volume. In order to more completely prevent elution ofcontaminants, it is more preferred that the oxygen permeability be lessthan or equal to 0.005 ml/day/container when converted to a 500 mlvolume. In order to make the oxygen permeability less than or equal to0.010 ml/day/container when converted to a 500 ml volume, thecharacteristics of the DLC film such as the composition and filmthickness and the like may be appropriately adjusted. However, in anycase, if the oxygen permeability is not made less than or equal to 0.010ml/day/container when converted to a 500 ml volume, the container willnot have sufficient contaminant elution barrier properties.

In accordance with the invention described in claim 1, by coating theinner surface of the container with a DLC film to give the containercontaminant elution barrier properties, it is possible to reuse used PETcontainers for foods and beverages. Further, in accordance with thereuse of PET containers becoming possible, the resin of used PETcontainers for foods and beverages can be placed in a recycling route.Additionally, the resin of used PET containers for foods and beveragesis reused without requiring excessive costs, namely, without carryingout a solid phase polymerization process on the resin of used PETcontainers.

In accordance with the invention described in claim 2, {circle over (1)}the resin of used PET containers which has not undergone intrinsicviscosity adjustment is used in a range that does not make it difficultto maintain container strength and ensure moldability, and {circle over(2)} the effects of colored impurities contained in the resin of usedPET containers for foods and beverages is minimized, and by consideringthe balance between the utilization factor of used PET for foods andbeverages and the performance of PET containers for foods and beveragescontaining recycled resin, it is possible to provide a DLC film coatedPET container for foods and beverages containing recycled resin havingan optimum compounding ratio.

In accordance with the invention described in claim 3, it is possible toprovide a DLC film coated PET container for foods and beveragescontaining recycled resin which has sufficient contaminant elutionbarrier properties, and which has sufficient fundamental containerproperties such as gas barrier properties and the like.

In accordance with the invention described in claim 4, it is possible toprovide a method of manufacturing a DLC film coated PET container forfoods and beverages containing recycled resin which has sufficientcontainer strength and sufficient contaminant elution barrierproperties, wherein a sufficient amount of unused PET resin pellets ismixed in to make it possible to mold a container using inexpensivepelletized resin of used PET containers for foods and beverages whichhas not undergone a solid phase polymerization process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing one example of a manufacturing apparatus formanufacturing a plastic container of the present invention.

The applied symbols in FIG. 1 are as follows: 1 is a base, 1A is anexhaust outlet, 2 is a shoulder portion electrode, 3 is a body portionelectrode, 4 is a bottom portion electrode, 5 is a plastic container, 6is an insulator, 7 is an O-ring, 8 is an interface device, 9 is ahigh-frequency oscillator, 10 is a housing portion, 11 is an innerelectrode, and 12 is a pipeline.

PREFERRED EMBODIMENTS OF THE INVENTION

Hereinbelow, a description will be given for the preferred embodimentsof a plastic container in which a DLC film is formed of the presentinvention.

FIG. 1 is a drawing showing one example of a manufacturing apparatus forforming a DLC film on the inner surface of a plastic container. As shownin FIG. 1, the present apparatus is equipped with a base 1, a shoulderportion electrode 2 and a body portion electrode 3 mounted to the base1, and a bottom portion electrode 4 which can be connected to anddisconnected from the body portion electrode 3. Further, the bottomportion electrode 4 isn't an electrode for only the bottom portion ofthe plastic container, and also functions as an electrode at the sideportion of the lower portion of the body. As shown in FIG. 1, theshoulder portion electrode 2, the body portion electrode 3 and thebottom portion electrode 4 each have inner wall surfaces shaped like theouter shape of a plastic container 5, in which the shoulder portionelectrode 2 is arranged along the shoulder portion of the plasticcontainer 5, the body portion electrode 3 is arranged along the bodyportion of the plastic container 5, and the bottom portion electrode 4is arranged along the bottom portion of the plastic container 5. Theshoulder portion electrode 2, the body portion electrode 3 and thebottom portion electrode 4 form the outer electrodes of the presentapparatus.

When the bottom portion electrode 4 is mounted to the body portionelectrode 3, the base 1, the shoulder portion electrode 2, the bodyportion electrode 3 and the bottom portion electrode 4 form a mutuallyairtight mounted state, and these function as a vacuum chamber equippedwith a housing portion 10 for housing the plastic container 5. As shownin FIG. 1, an insulator 6 is provided between the shoulder portionelectrode 2 and the body portion electrode 3, and in this way theshoulder portion electrode 2 and the body portion electrode 3 areelectrically insulated from each other. Further, an O-ring 7 is providedbetween the body portion electrode 3 and the bottom portion electrode 4,and when the bottom portion electrode 4 is mounted, a small gap isformed between the bottom portion electrode 4 and the body portionelectrode 3. In this way, while ensuring airtightness between the bottomportion electrode 4 and the body portion electrode 3, electricalinsulation is carried out between both electrodes.

An inner electrode 11 is provided in the housing portion 10, and theinner electrode 11 is inserted into the inside of the plastic container5 housed inside the housing portion 10. The inner electrode 11 iselectrically connected to a ground potential.

The inner electrode 11 is formed to have a hollow shape (tube shape),and one blowout hole (not shown in the drawing) which communicates theinside and the outside of the inner electrode 11 is formed in the lowerend thereof. Further, instead of providing a blowout hole in the lowerend, a plurality of blowout holes (not shown in the drawing) may beformed to pass through the inside and the outside of the inner electrode11 in the radial direction. A pipeline 12 which communicates with theinside of the inner electrode 11 is connected to the inner electrode 11,and this structure makes it possible for a source gas fed into theinside of the inner electrode 11 via the pipeline 12 to be emitted intothe inside of the plastic container 5 via the blowout hole. Further, thepipeline 12 is made of metal and has electrical conductivity, and asshown in FIG. 1, the pipeline 12 is used to connect the inner electrode11 to a ground potential. Further, the inner electrode 11 is supportedby the pipeline 12.

As shown in FIG. 1, the output terminal of a high-frequency oscillator 9is connected to the bottom portion electrode 4 via an interface device8. The high-frequency oscillator 9 generates a high-frequency voltagebetween itself and the ground potential, and in this way ahigh-frequency voltage is applied between the inner electrode 11 and thebottom portion electrode 4.

Next, a description will be given for the process when a DLC film isformed on the inner surface of the plastic container 5 using the presentapparatus.

The plastic container 5 is set so that the bottom portion thereof makescontact with the inner surface of the bottom portion electrode 4, and byraising the bottom portion electrode 4, the plastic container 5 ishoused in the housing portion 10. At this time, the inner electrode 11provided in the housing portion 10 is inserted inside the plasticcontainer 5 through the orifice (upper end opening) of the plasticcontainer 5.

When the bottom portion electrode 4 is raised to a prescribed positionto hermetically seal the housing portion 10, a state is formed in whichthe outer periphery of the plastic container 5 makes contact with theinner surfaces of the shoulder portion electrode 2, the body portionelectrode 3 and the bottom portion electrode 4. Next, the air inside thehousing portion 10 is exhausted through an exhaust outlet 1A of the base1 by a vacuum device not shown in the drawing. After the pressure insidethe housing portion 10 has been reduced to a required vacuum level, asource gas (e.g., carbon source gases such as aliphatic hydrocarbonssuch as acetylene and the like, aromatic hydrocarbons and the like, andhydrocarbon gases containing Si) supplied via the pipeline 12 isintroduced into the inside of the PET container 5 from the blowout holeof the inner electrode 11.

After the concentration of the source gas reaches a prescribed value,the high-frequency oscillator 9 (e.g., 13.56 MHz) is activated to applya high-frequency voltage between the inner electrode 11 and the outerelectrodes, whereby a plasma is generated inside the plastic container5. In this way, a DLC film is formed on the inner surface of the plasticcontainer 5.

Namely, the formation of a DLC film on the inner surface of the plasticcontainer 5 is carried out by a plasma CVD method, wherein electronsaccumulate on the inner wall surfaces of the outer electrodes insulatedby the plasma generated between the outer electrodes and the innerelectrode 11, and a prescribed fall in potential occurs.

In this way, the carbon and the hydrogen of the hydrocarbon that formsthe source gas present in the plasma are each ionized to positive, andthese ion randomly with the inner wall surface of the plastic container5 running along the inner wall surfaces of the outer electrodes, wherebyan extremely fine DLC film is formed on the inner wall surface of theplastic container 5 by the bonding between adjacent carbon atoms and thebonding between carbon atoms and hydrogen atoms, and by the breaking ofbonds of hydrogen atoms that have bonded once (sputtering effect).

As described above, the output terminal of the high-frequency oscillator9 is connected to only the bottom portion electrode 4. Further, a gap isformed between the bottom portion electrode 4 and the body portionelectrode 3, and the bottom portion electrode 4 and the body portionelectrode 3 are electrically insulated from each other. Furthermore, theinsulator 6 is provided between the body portion electrode 3 and theshoulder portion electrode 2, and the body portion electrode 3 and theshoulder portion electrode 2 are electrically insulated from each other.Accordingly, the high-frequency electric power applied to the bodyportion electrode 3 and the shoulder portion electrode 2 becomes smallerthan the high-frequency electric power applied to the bottom portionelectrode 4. However, because capacity coupling is carried out throughthe respective gaps between the bottom portion electrode 4 and the bodyportion electrode 3, and between the body portion electrode 3 and theshoulder portion electrode 2, a certain degree of high-frequencyelectric power is also applied to the body portion electrode 3 and theshoulder portion electrode 2.

In general, the bottom portion of plastic containers such as bottles andthe like have complex shapes, and it is difficult to form a DLC filmhaving sufficient thickness. Further, because the bottom portion hasinsufficient drawing at the time of manufacturing, the gas barrierproperties of the plastic itself become lower at the bottom portion. Forthis reason, even after the DLC film is formed, the gas barrierproperties of the bottom portion of the container are prone to lowering.However, by means of the manufacturing apparatus shown in FIG. 1,because it is possible to apply high-frequency electric power largerthan that for the body portion and shoulder portion to the bottomportion of the plastic container, it is possible to form a DLC filmhaving a uniform thickness for the entire container, and it is possibleto form a thicker DLC film at the bottom portion where the gas barrierproperties of the plastic itself are low. Accordingly, it is possible toeffectively improve the gas barrier properties for the entire container.In the embodiment described above, it is possible to raise the appliedelectric power to 1200˜1400 W for example, and accordingly it ispossible to plan a reduction in manufacturing costs due to theshortening of the coating time.

In the apparatus described above, the shoulder portion electrode 2, thebody portion electrode 3 and the bottom portion electrode 4 areconstructed so as to be completely insulated against direct current, butit is also possible to connect each of the electrodes to each other byresistance or capacitive elements or the like. In short, so long as itis possible to apply high-frequency electric power having a requiredstrength in accordance with each portion of the container, for example,a plurality of high-frequency oscillators may be provided to applyhigh-frequency electric power separately to each of the electrodes ofthe shoulder portion electrode 2, the body portion electrode 3 and thebottom portion electrode 4, or the output of a single high-frequencyoscillator may be connected to each of the electrodes via a plurality ofinterface devices.

Further, in the apparatus described above, an example was described forthe case where the outer electrodes are divided into three portions, butthe outer electrodes may be divided into two portions, or the outerelectrodes may be divided into four or more portions.

The DLC film coated plastic container of the present invention can beused ideally as a returnable container, but can also be used for one-wayuse (i.e., the use of a disposable container which is filled withcontents only one time and not recycled).

The method of manufacturing the DLC film coated plastic container is notlimited to the method described above. In the embodiment describedabove, a plasma CVD method that uses high frequency is used, but it isalso possible, for example, to use a plasma CVD method using microwaves.

EXAMPLE EMBODIMENTS Example Embodiment 1

A description will be given for the results of testing the effectivenessof contaminant elution inhibition of PET containers for foods andbeverages containing recycled resin.

Because used PET in the city is found in various contaminated states,model contaminants were mixed with unused PET flakes to form PET flakescontaminated with model contaminants, and pseudo used PET pellets werecreated, and then these pseudo used PET pellets and unused PET pelletswere used to form a container which was then evaluated.

In general, the contaminants of plastic can be thought to form thefollowing four types of substances: {circle over (1)} substances whichare volatile and polar; {circle over (2)} substances which are volatileand nonpolar; {circle over (3)} substances which are nonvolatile andnonpolar; and {circle over (4)} substances which are nonvolatile andpolar. In this test, {circle over (1)} toluene (C₆H₅ CH₃, hydrocarbon,volatile, nonpolar), {circle over (2)} chlorobenzene (C₆H₅ Cl,halogenated hydrocarbon, volatile, intermediate polarity, aggressivechemical for PET), {circle over (3)} n-docosane (C₂₂H₄₆, hydrocarbon,nonvolatile, nonpolar), and {circle over (4)} nonadecanol (CH₃(CH₂)₁₈OH,alcohol, nonvolatile, having polarity) were used as the modelcontaminants for each of the four types described above.

A. Manufacture of Pseudo Used PET Pellets

First, new PET containers were shredded to create unused PET flakes.Next, the four types of model contaminants described above were added tothe unused PET flakes. Specifically, as a first mixing operation,prescribed amounts of the four types of model contaminants were mixedwith 500 g of unused PET flakes to make PET flakes contaminated with themodel contaminants. After that, as a second mixing operation, 500 g ofthe PET flakes contaminated with the model contaminants was furthermixed with 4500 g of unused PET flakes to make 5000 g of a PET flakemixture contaminated with the model contaminants in which prescribedamounts of the model contaminants were mixed inside the PET. Table 1shows the mixture amounts of the model contaminants and the PET flakes.TABLE 1 Model Contaminants Contamination PET Flakes (g) LevelContaminants (g) First Mixing Second Mixing Low 1 g Each × 4 = 4 g 5004,500 Concentration Intermediate 3 g Each × 4 = 12 g 500 4,500Concentration High 10 g Each × 4 = 40 g 500 4,500 Concentration

As shown in Table 1, mixtures were made for the three types ofconcentrations of model contaminants defined as low concentration,intermediate concentration and high concentration. With respect to the5000 g of PET flakes, 1 g of each of the model contaminants for a totalof 4 g for the low concentration, 3 g of each of the model contaminantsfor a total of 12 g for the intermediate concentration, and 10 g of eachof the model contaminants for a total of 40 g for the high concentrationwere ultimately present in the mixtures. In the low concentrationmixture, there was 0.02 parts by weight of each of the modelcontaminants with respect to 100 parts by weight of the PET flakes. Inthe intermediate concentration mixture, there was 0.06 parts by weightof each of the model contaminants with respect to 100 parts by weight ofthe PET flakes. In the high concentration mixture, there was 0.20 partsby weight of each of the model contaminants with respect to 100 parts byweight of the PET flakes.

Next, these three types of PET flakes contaminated with the modelcontaminants at the low concentration, intermediate concentration andhigh concentration were held at 50° C. in a hermetically sealedcontainer for two weeks to force the model contaminants to adsorb ontothe PET flakes. Next, the PET flakes contaminated with the modelcontaminants were remelted by an extruder to make pseudo used PETpellets. By carrying out this remelting process, the intrinsic viscosityof the pseudo used PET pellets were lowered. In this regard, in order toraise the intrinsic viscosity of the pseudo used PET pellets, namely inorder to increase the molecular weight of the pseudo used PET pellets,solid phase polymerization was carried out inside a flow of nitrogen gasunder the conditions of 230° C. for three hours.

Next, in order to examine the reduction of contaminants due to thepurification process, analysis of the contamination level was carriedout for the PET flakes (denoted as “Flakes”) contaminated with the modelcontaminants, the pseudo used PET pellets (denoted as “Pellets”) and thepellets after solid phase polymerization (denoted as “After Solid PhasePolymerization”). First, 1 g samples, namely the pseudo used PET flakemixture, the pseudo used PET pellets and the compounded PET pellets wereplaced in 5 ml test tubes, and then 1 ml of1,1,1,3,3,3,-hexafluoro-iso-propanol was added to each sample. Thesamples were held at 60° C. for 24 hours in order to expand the PET.Then, 2 ml of iso-propanol was added, and after being held at 60° C. for24 hours, the contaminants were extracted. Next, the extracts wereanalyzed by a gas chromatography method using a FID detector. The gaschromatograph was a HP5890 I I, and the column used a SE10-30 m-0.32 mmi.D.−0.32 μm film thickness. The measurement accuracy was 0.4 ppm, anddetection was not possible below 0.4 ppm. The contamination levels areshown in Table 2. TABLE 2 Toluene Chlorobenzene n-Docosane NonadecanolContamination Volatile Volatile Nonvolatile Nonvolatile Level ProcessNonpolar Polar Nonpolar Polar Low Flakes 20 43 25 18 ConcentrationPellets Not Detected 2.0 15 4.3 After Solid Phase Not Detected NotDetected 0.8 1.3 Polymerization Intermediate Flakes 63 98 43 75Concentration Pellets Not Detected 6.3 28 37 After Solid Phase NotDetected Not Detected 1.5 4.0 Polymerization High Flakes 89 156 85 250Concentration Pellets Not Detected 9.2 42 50 After Solid Phase NotDetected Not Detected 3.5 63 PolymerizationUnits: ppm

As shown in Table 2, toluene which is a volatile substance was forcedout due to heating up to a temperature above the melting point(approximately 255° C.) at the time of remelting in the extruder, andcould not be detected at the pelletization step. Further, chlorobenzenewhich is a volatile substance was forced out at the solid phasepolymerization step (three hours at 230° C. in a flow of nitrogen gas),and could not be detected. The n-docosane and the nonadecanol which arenonvolatile substances remained even after solid phase polymerization.

B. Evaluation by Container Formation

Next, a description will be given for the formation of containers. Whilecarrying out mixing to form 0.10, 0.20, 0.30, 0.40 and 0.60 compoundingratios (weight of pseudo used PET pellets/(weight of pseudo used PETpellets+weight of unused PET pellets)) of the intermediate concentrationpseudo used PET pellets before the solid phase polymerization describedin A and the unused PET pellets, trial contaminated PET containers(resin weight: 32 g) having a 500 ml volume were created by injectionmolding (this case is denoted as “I”). The molding temperature wasapproximately 270° C. The compounding conditions of the pellets at thecontainer molding time are shown in Table 3. TABLE 3 Pellet CompoundingConditions at Container Molding Time Amount Amount of Added of AddedObtained Pseudo Unused Container Amount of Each Contaminant Used PET PETMolding Added Per 5000 g of Pseudo Compounding Pellets Pellets WeightUsed PET Pellets Ratio (g) (g) (g) (g) 0.10 3.2 28.8 32 3 g Each × 4 ×0.1 = 1.2 g 0.20 6.4 25.6 32 3 g Each × 4 × 0.2 = 2.4 g 0.30 9.6 22.4 323 g Each × 4 × 0.3 = 3.6 g 0.40 12.8 19.2 32 3 g Each × 4 × 0.4 = 4.8 g0.60 19.2 12.8 32 3 g Each × 4 × 0.6 = 7.2 g

Further, these compounding ratios (weight of pseudo used PETpellets/(weight of pseudo used PET pellets+weight of unused PETpellets)) are compounding ratios that correspond to the compoundingratios (weight of recycled resin of used PET containers for foods andbeverages which has not undergone intrinsic viscosity adjustment/(weightof recycled resin of used PET containers for foods and beverages whichhas not undergone intrinsic viscosity adjustment+weight of unused PETresin)) in the case of recycling actual used PET containers.

Next, using only the low concentration, intermediate concentration andhigh concentration pellets after solid phase polymerization as shown inTable 2 (this case is denoted as “II”), trial contaminated PETcontainers (resin weight: 32 g) having a 500 ml volume were created byinjection molding.

Then, using the DLC film forming apparatus described above, a DLC filmwas formed on the inner wall surfaces of the contaminated PET containerscreated by I and II described above to create DLC film coated containershaving a 500 ml volume.

As for the method of forming the DLC film, the method of applyinghigh-frequency electric power to the bottom electrode 4 was used as anelectric discharging method with acetylene used as the source gas.Namely, in the state in which the shoulder portion electrode 2, the bodyportion electrode 3 and the bottom portion electrode 4 are electricallyinsulated from each other, high-frequency electric power at 13.56 MHzwas applied only to the bottom portion electrode 4. The high-frequencyelectric power was 1300 W, the vacuum level was 0.05 torr (6.66 Pa), andthe gas flow rate was 31 cc/min.

The average thickness of the DLC film coated containers wasapproximately 0.3 mm, the film thickness of the DLC film was 200˜300 Å,and the amount of oxygen permeation for an entire DLC film coatedcontainer was 0.003 ml/day/container. Further, the amount of oxygenpermeation in the PET containers having the same 500 ml volume but noDLC film formed therein was 0.033 ml/day/container for an entirecontainer.

Next, a description will be given for the contaminant elution test forthe above-described “contaminated PET containers” and the “DLC filmcoated containers” which are contaminated PET containers coated with aDLC film.

Each of the contaminated containers and the DLC film coated containerswas filled with 50 ml of 1,1,1,3,3,3,-hexafluoro-iso-propanol, and thenmixing by shaking was carried out at 60° C. for 24 hours to expand thePET. Next, 100 ml of iso-propanol was added, and mixing by shaking wascarried out at 60° C. for 24 hours to extract the contaminants. Then,after concentrating the 150 ml of extracted liquid to 20 ml, analysiswas carried out by a gas chromatograph.

Table 4 shows the analysis results of the contaminants extracted fromthe contaminated containers and the DLC film coated containers for thecase of I and II. Further, in Table 4, n-docosane is denoted by “D”, andnonadecanol is denoted by “N”. TABLE 4 Used DLC Film MoldingContamination Compounding Contaminated Coated Contaminant Material LevelRatio PET Container Container D I Intermediate 0.10 50 Not DetectedConcentration D I Intermediate 0.20 97 Not Detected Concentration D IIntermediate 0.30 120 Not Detected Concentration D I Intermediate 0.40Moldability Δ Moldability Δ Concentration D I Intermediate 0.60Moldability x Moldability x Concentration D II Low 1.00 16 Not DetectedConcentration D II Intermediate 1.00 28 Not Detected Concentration D IIHigh 1.00 72 Not Detected Concentration N I Intermediate 0.10 43 NotDelected Concentration N I Intermediate 0.20 102 Not DetectedConcentration N I Intermediate 0.30 153 Not Detected Concentration N IIntermediate 0.40 Moldability Δ Moldability Δ Concentration N IIntermediate 0.60 Moldability x Moldability x Concentration N II Low1.00 24 Not Delected Concentration N II Intermediate 1.00 56 NotDetected Concentration N II High 1.00 97 Not Detected ConcentrationUnits: μg/500 ml PET Container

The detection limit was 10 μg. In the case of I, the polymerizationdegree of the pseudo used PET pellets went down, and the intrinsicviscosity was lowered. Accordingly, in the case of the compoundingratios 0.40 and 0.60 which contain a lot of these pseudo used PETpellets having lowered intrinsic viscosity, the container strength isnot sufficient, and the container moldability is also poor. When acompounding ratio of 0.40 is not exceeded, the container will havesufficient strength, and the container moldability will also be good. Asshown in Table 4, among the cases having good container moldability,both n-docosane and nonadecanol were detected for all the contaminatedPET containers. On the other hand, in the DLC film coated containers,there was no detection of either n-docosane or nonadecanol for any ofthe contamination levels. In this way, by forming a DLC film on theinner wall surface of PET containers, it is possible to effectivelyinhibit the elution of contaminants from the PET containers. Further,both toluene and chlorobenzene which are volatile substances werereduced to nondetectable levels at the contaminated PET container stepas described above, and the extraction thereof from the contaminatedcontainers and the DLC film coated containers was not detected.

From the facts given above, in the case where used PET is recycled tomanufacture containers again, by carrying out solid phase polymerizationto raise the polymerization degree of used PET, it is possible forcontainers to use 100% used PET. However, because a rise inmanufacturing costs will accompany the carrying out of solid phasepolymerization of used PET, preferably used PET resin which has notundergone solid phase polymerization is mixed with unused PET resin tocarry out container molding, and as a more preferred state, thecompounding ratio (weight of recycled resin of used PET containers forfoods and beverages which has not undergone intrinsic viscosityadjustment/(weight of recycled resin of used PET containers for foodsand beverages which has not undergone intrinsic viscosityadjustment+weight of unused PET resin)) should be greater than 0 butless than 0.40. Preferably, the compounding ratio should be greater than0 but less than or equal to 0.30. When considering the utilizationfactor of used PET and the performance of PET containers for foods andbeverages containing recycled resin, the most preferred compoundingratio is greater than or equal to 0.10 but less than or equal to 0.20.

Example Embodiment 2

Next, with reference to the case of II of Table 4, a description will begiven for the relationship between the oxygen permeability of the DLCcontainers and the amount of elution of the contaminants.

First, using the high concentration pellets after solid phasepolymerization, a contaminated PET container (Experiment Number 1, noDLC film coating) having a 500 ml volume was created, and by changingthe above-described vapor deposition conditions for the inner wallsurface of the contaminated PET to form a DLC film on the inner wallsurfaces of contaminated PET containers, a plurality of DLC containers(Experiment Numbers 2˜9) having different oxygen permeabilities werecreated.

As shown in Table 5, the oxygen permeability of the contaminated PET(Experiment Number 1) in a state where a DLC film was not formed was0.033 ml/day/container. Further, the oxygen permeabilities of the DLCcontainers (Experiment Numbers 2˜9) created by changing the vapordeposition conditions were respectively 0.020 ml/day/container(Experiment Number 2), 0.015 ml/day/container (Experiment Number 3),0.012 ml/day/container (Experiment Number 4), 0.010 ml/day/container(Experiment Number 5), 0.008 ml/day/container (Experiment Number 6),0.005 ml/day/container (Experiment Number 7), 0.003 ml/day/container(Experiment Number 8), and 0.001 ml/day/container (Experiment Number 9).Table 5 shows the results of analyzing the amount of elution ofnonadecanol using the same method as that of Example Embodiment 1. TABLE5 Amount of Oxygen Nonadecanol Permeability Elution Experiment ml/Day/μg/500 ml Number Container PET Container 1 Not Having DLC Process 0.03395 2 Having DLC Process 0.020 30 3 Having DLC Process 0.015 18 4 HavingDLC Process 0.012 12 5 Having DLC Process 0.010 Not Detected 6 HavingDLC Process 0.008 Not Detected 7 Having DLC Process 0.005 Not Detected 8Having DLC Process 0.003 Not Detected 9 Having DLC Process 0.001 NotDetected

As shown in Table 5, in the contaminated PET (Experiment Number 1) whichwas not formed with a DLC film and in the DLC film coated containers(Experiment Numbers 2˜4) which have an oxygen permeability greater thanor equal to 0.012 ml/day/container, eluted nonadecanol was detected, butin the DLC film coated containers (Experiment Numbers 5˜9) which have anoxygen permeability less than or equal to 0.010 ml/day/container,nonadecanol was not detected. Accordingly, it is understood that bycoating the DLC film so that the oxygen permeability in the DLC coatedcontainers is less than or equal to 0.010 ml/day/container, it ispossible to almost completely prevent elution of contaminants.

By the facts described above, in contaminated PET containers, oneportion of contaminants will elute into the container contents.Accordingly, contaminated PET containers can not be reused in a statewhere only molding is carried out. In the present invention, thejudgment of whether or not the DLC film has sufficient contaminantelution barrier properties was determined by indicating the oxygen gasbarrier properties of the entire container, and when the oxygenpermeability of contaminated PET containers coated with a DLC film isless than or equal to 0.010 ml/day/container when converted to a 500 mlvolume, it was discovered that it is possible to almost completelyprevent elution of contaminants. In order to more completely preventelution of contaminants, it is more preferred that the oxygenpermeability be less than or equal to 0.005 ml/day/container whenconverted to a 500 ml volume. In order to make the oxygen permeabilityless than or equal to 0.010 ml/day/container when converted to a 500 mlvolume which was discovered to make such fact possible, thecharacteristics of the DLC film such as the composition and filmthickness and the like may be appropriately adjusted. However, in anycase, if the oxygen permeability is not made less than or equal to 0.010ml/day/container when converted to a 500 ml volume, the container willnot have sufficient contaminant elution barrier properties.

From Example Embodiment 1 and 2, the DLC film coated PET container forfoods and beverages containing recycled resin according to the presentinvention is a container molded from molding material which is a mixtureof resin of used PET containers for foods and beverages and unused PETresin, wherein the compounding ratio of the mixture is preferablygreater than 0 but less than 0.40, and wherein the oxygen permeabilityof the container converted to a 500 ml PET container is preferably lessthan or equal to 0.010 ml/day/container.

Further, the containers having a compounding ratio less than 0.40 of theexample embodiments received almost no effects from contained coloredimpurities at the time container molding was carried out using resin ofused PET containers for foods and beverages.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. A method of manufacturing aDLC film coated PET container for foods and beverages containingrecycled resin, comprising the steps of: shredding used PET containersfor foods and beverages to form flakes, and then removing foreignmaterial from said flakes, washing said flakes using an alkaline washingagent and water, and drying said flakes to obtain washed flakes;obtaining recycled pellets which have not undergone intrinsic viscosityadjustment from said washed flakes; molding a container containingrecycled resin using said recycled resin pellets and un used PET resinpellets adjusted so that the compounding ratio (weight of recycled resinpellets/weight of recycled resin pellets+weight of unused PET resinpellets) is greater than 0 but less than 0.40; and coating the innersurface of said container with a DLC film so that oxygen permeability ofsaid container is less than or equal to 0.01 ml/day/container whenconverted to a 500 ml volume.
 5. A method of manufacturing a DLC filmcoated PET container for foods and beverages containing recycled PETresin as defined in claim 4 wherein said film coated PET containercomprises from 10% to 40% of recycled PET.